Pulmonary vein ablation is a known surgical treatment for atrial fibrillation (AF). Current solutions are based on a single energy source e.g. RF, cryogenic, ultrasound, laser or microwave. Each modality has its own advantages and disadvantages both in terms of tissue interaction or delivery method.
In order to optimize the treatment, a uniform transmural lesion must be created in the target tissue. Overtreatment may result in irreversible collateral thermal or mechanical damage to surrounding tissue which may lead to perforation or other complications while insufficient lesion creation may not electrically isolate the PV from the left atrium wall. With some of the technologies available today, due to the nature of the treatment modality, it is difficult to determine at what point the treatment desired is sufficiently administered.
For example, in a known treatment technique using a cryogenic fluid, the fluid is introduced into a balloon catheter which may be positioned within the pulmonary vein (PV). From experience and prior knowledge the operating doctor may have determined the length of time the fluid should be in contact with the tissue to achieve the desired ablation and creation of a lesion in the tissue. However, this may be imprecise and can vary from doctor to doctor and with the patient's tissue makeup. Further, introduction of the cryogenic fluid, its withdrawal, and stopping the creation of the lesion is imprecise given that the cooling of the tissue is gradual and to some extent not precisely controllable. Thus, there remains a need to provide an ablation system that permits more precise control of the creation of a lesion and for controllably halting the extent of the damage created by the lesion.
Another example is the creation of a lesion using radio frequency (RF) energy. Typically, unlike a cryogenic solution, in the treatment of AF using a RF source, a balloon is not used, but rather a catheter with one or more electrodes is introduced into the PV and the electrodes activated. Again, as in the example of the cryogenic treatment, the duration of treatment and the extent of damage caused by the application of RF may be imprecise and only loosely controllable. Thus, there is a need to provide a RF ablation system that permits more precise control and monitoring of a lesion created by the application of RF energy.